Electron sorting devices



Jan. 15, 1963 I J. M. OSEPCHUK 3,073,991

ELECTRON SORTING DEVICES Filed Sept 29, 1958 5 Sheets-Sheet 1 INVENTOR lJOHN M. OSEPCHUK ATTORNEY Jan. 15, 1963 J. M. OSEPCHUK ELECTRON SORTINGDEVICES 5Sheecs-Sheet 2 Filed Sept. 29, 1958 lEna FIG. 3

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llvvnvroR' JOHN M. OSEPCHUK Jan. 15, 1963 J. M. OSEPCHUK 3,073,991

ELECTRON SORTING DEVICES Filed Sept. 29, 1958 5 Sheets-Sheet 3 SORT/N6PEG/0N PERTURBAT/ON REG/0N IN TERACT/O/V PEG/0N INVENTOR v JOHN M.OSE'PCHUK v MM ATTORNE) Jan. 15, 1963 J. M. OSEPCHUK 3,073,991

ELECTRON SORTING DEVICES Filed Sept. 29, 1958 5 Sheets-Sheet 4 SORT/N6"REG/01V INTERACTION REG/ON l f I su/v PER TURBA TION PEG/0N REG/0N l/VVf/V TOP JOHN M. OSEPCHUK FIG. 8 /WM M A T TOR/YE Y Jan. 15, 1963 J. M.OSEPCHUK 3,073,991

ELECTRON SORTING DEVICES Filed Sept. 29, 1958 5 Sheets-Sheet 5 FIG 90l0,

c1 :1 I: :1 1:1 63 1:1 1:1 97 E GB 981, .96 93 INVENTOP JOHN M. OSEPCHUKATTORNEY 3,073,991 ELECTRON SORTENG DEVICES John M. Osepchuk, Waltham,Mass, assignor to Raytheon Company, Lexington, Mass, a corporation ofDelaware Filed Sept. 29, 1958, Ser. No. 763,856 14 Claims. (Cl. 315-393)This invention relates in general to an electron sorting device forproducing a density modulated electron beam and is particularlyconcerned with a device utilizing the interaction between a travelingelectromagnetic wave and an electron beam moving in synchronism with acomponent of the wave and in which the interaction occurs in an'unvarying electric field having its lines of force at right angles toan unvarying magnetic field. The invention has general utility inelectronic apparatus utilizing a density modulated electron beam.

The invention contemplates utilizing a phenomenon denoted electronsorting to initiate modulation of an electron beam. In an electronsorting device, electrons having an orbital component of motion areinjected into a high frequency field in such a manner that the electronsfollow a generally arcuate trajectory while moving in synchronism withthe phase velocity of the electromagnetic wave associated with the highfrequency field. The influence of the high frequency field causes someelectrons to move upwardly with respect to the field and other electronsto move downwardly. Those electrons which move downwardly are absorbedby a negatively polarized electrode and thus are removed from the streamof electrons injected into the field. The result of this electronsorting mechanism is a density modulation of the electron stream sincesome segments of the stream have a deficiency of electrons. Theelectrons remaining in the stream are caused to further interact withthe high frequency field and progressively deliver energy to that fieldwhereby the electron sorting mechanism, once initiated, isself-sustaining.

The invention finds immediate employment in high frequency oscillatoryand amplifying devices which utilize the prolonged inter-action betweena stream of .charged particles and a guided electromagnetic wavetraveling along a wave retardation circuit. Devices of this type arecustomarily designated traveling wave tubes. Traveling wave tubesemploying crossed electric and magnetic fields are commonly termedM-type tubes. M-type tubes may be operated as amplifiers or oscillatorsand may be further classified as either forward wave tubes or backwardwave tubes. In a backward wave tube, the electron beam travels at avelocity which is synchronous with the phase velocity of a travelingwave space component moving in a direction opposite to that of theenergy flow along the wave circuit. That is, a backward wave tube ischaracterized by an electron beam traveling in one direction and theenergy of the induced wave traveling in the opposite direction. In aforward wave tube, the electron beam and the energy of the induced wavecharacteristically travel in the same direction.

A baclmard wave tube is customarily provided with a wave retardationline, more usually termed a delay line, constructed so that the phasevelocity of the fundamental wave travels in a direction inverse to thedirection of the group velocity. A forward wave tube, incontradistinction, is provided with a delay line constructed so that thephase velocity of the fundamental wave is in the same direction as thegroup velocity. The fundamental wave is defined as that component of awave having the largest phase velocity.

The usual crossed field type of traveling wave tube utilizes anelongated delay line spaced from a coextensive electrode, known as thesole and a DC. field is impressed between the delay line and the sole insuch a manner that the delay line constitutes the positive elec-3,073,991 Patented Jan. 15, 1963 ice trode and the sole constitutes thenegative electrode. The space between the delay line and the sole isdenoted as the interaction region. In order to achieve maximumefiiciency in M-.type tubes, an electron beam, emanating from anelectron gun, is projected into the interaction space in a mannerintended to cause the beam to follow a linear path through theinteraction region. Bunching of electrons in the beam (beam modulation)is caused by a phenomenon known as phase focusing which has beenanalyzed and is documented in the technical literature e.g. the articleentitled, Fundamental Phenomena in Traveling Wave Tubes appearing inLOnde Elec trique No. 325, April 1954. In the conventional M- type tubethe electron beam enters the interaction region initially unmodulatedand modulation of the beam by phase focusing occurs progressively in theinteraction region together with the induction of H.'F. (high frequency)currents in the delay line. Because phase focusing has heretofore beenutilized exclusively as the initial mechanism for modulating theelectron beam it has not been feasible to build a traveling wave tubehaving a negatively polarized delay line because negative polarinationof the line causes unfavorable phase focusing of the beam. That is, witha negative delay line the phenomenon ofphase focusing opposes favorablebunching of electrons in the beam.

This invention includes utilizing the phenomenon denoted electronsorting to commence modulation of the electron beam in M-type tubes. Byemploying electron sorting rather than phase focusing, it has been foundto be feasible to construct an M-type traveling wave tube employing anegatively polarized delay line. In positive line tubes the mechanism ofelectron sorting is employed to aid the normal phase focusing modulationof the beam. By means of electron sorting there is introduced .acontrolled initial modulation of the beam at the appropriate highfrequency. A successful realization of a negative line tube isparticularly advantageous, since efficient operation of such a tubecauses much of the beam current to flow to the positive electrode and tothe collector electrode and the beam current which does flow to the:delay line arrives with low kinetic energy. For this reason, a negativeline tube avoids the problems and power limits concerned with the heatdissipation capabilities of positive delay lines in which an appreciableportion of .the beam current normally flows in the delay line. Anegative line traveling wave tube employing beam sorting now makespossible the realization of a high powered device for amplifying andgenerating wave energy in the millimeter and centimeter wave lengthregions.

The nature of the present invention, together with its various featuresand advantages, can be more readily understood by perusal of thefollowing detailed description when considered in conjunction with theillustrative embodiments shown by the accompanying drawings in which:

FIG. 1 diagrammatically illustrates the phase focusing action whichoccurs with relation to a positively polarized delay line;

FIG. 2 diagramatically illustrates the electron sorting mechanism withrelation to a positively polarized delay line;

FIG. 3 diagrammatically illustrates the phase focusing action occurringin relation to .a negatively polarized delay line;

FIG. 4 diagrammatically illustrates the electron sorting mechanism withrelation to a negatively polarized delay line;

FIG. 5 represents electron sorting in a high frequency field supported.by a modulated electron beam;

FIG. 6 represents an elemental form of traveling wave tube employingelectron sorting;

FIG. 7 is a schematic representation of a traveling wave tube having apositively polarized delay line and in which the mechanism of electronsorting is employed;

FIG. 3 is a schematic representation of a traveling wave tube having anegatively polarized delay line and in which the mechanism of electronsorting is employed to provide initial modulation of the electron beam;

FIG. 9 illustrates a modification of the tube shown in FIG. 8;

FIG. 10 schematically depicts a traveling wave tube having twooppositely polarized delay lines and in which the mechanism of electronsorting is employed;

FIG. 1 -l shows, in schematic form, an improvement upon the tube shownin FIG. 10; and

FIG. 12 depicts another type of traveling wave tube employing electronsorting.

Referring now to FIG. 1, which diagrammatically illustrates the forcelines of the high frequency field of a travelling electromagnetic waveas they would appear to an electron moving with a translational velocityV which is equal to-the velocity of a space harmonic of the wave, thereis shown a delay line 1 of the interdigital type along which the wavepropagates, and a sole electrode 2 spaced from the relayline. Anunvarying electric field E is established between the delay line and thesole by impressing a positive potential on the delay line. 7 Anunvarying magnetic field B is established at right angles to the D.C.electric field to cause electrons subject to the action of the crossedfields to move in a desired direction, from left to right for example,at an average velocity t The dashed line 3 represents an equipoten-tialsurface along which electrons are introduced at the average velocity VAssuming that a component of a high frequency wave is propagating alongthe delay line, the lines of force of its field are displaced in spaceat the phase speed of the wave component. That is, the HF. field movesalong the delay line, from'left to right for example, at a speed whichis equal to the phase velocity of the wave component. To an electronmoving with the same velocity as the phase velocity of the travelingwave component, however, the field appears to be stationary. It will beseen from FIG. 1 that the transverse component E of the HF. field in theregions a and c is in the same direction as the electric field E and thetransverse component E in the region b ,is opposed to the electric fieldE so that the resultant field becomes alternately weaker at b andstronger at a and c than the D.C. field.

' ,Two components of the high frequency field come into play in theinteraction mechanism between electrons and the traveling wave. Thetransverse component E of the HF. field accelerates or decelerates,according to its direction, the electrons velocity parallel to the delayline and bring electrons in the field into a position such that they arebunched in the favorable phase and are subjected to a force which pushesthem towards the anode without changing their longitudinal speed,thereby causing the electrons to 'give up part of their potential energyto the HF. field. It is seen thus, that the normal phase focusing actionwhich is present in'a traveling wave tube having a positive delay lineisaccomplished by redistributing the electrons in the HF. field so thatthose electrons which initially were in an unfavorable phase are movedinto a favorable phase. This can be more fully appreciated byconsidering an electron, having an initial rectilinear trajectory, thatis, an electron having no orbital motion, which is injected at point 4in FIG. 1 into the interaction space between delay line 1 and sole 2.Since the'transverse H.F. field component E at point 4 reinforces thefield E the electron is accelerated'vand, as electrons in an electricfield tend to responds to a favorably phased electron.

move perpendicularly to lines of force of the field, the electron movesalong the curve 5 toward the delay line delivering its potential energyto the HF. field. An electron at point 6 is subjected to a deceleratingforce because the transverse HF. field component E now opposes theconstant field E therefore the electron at point 6 is slowed down andmoves along the curve 7 toward the delay line. A similar analysis showsthat an electron at point 8 will move along the curve 9 toward the delayline. Thus, phase focusing causes a bunching of electrons in the beam inthe favorable phase.

An electron at point 10 in FIG. 1 is in the more unfavorable phase sincethe action of .the RF. field causes that electron to move downwardlytoward the sole 2. The sole, however, in a conventional traveling waveM-type tube, is usually maintained sufliciently negative so that none oronly a small fraction of electrons strike the sole and are absorbed.

The mechanism of electron sorting is distinct from phase focusing inthat Where electron sorting is employed 'most of the unfavorably phasedelectrons are removed stood by considering that an electron following acycloidal trajectory is, in its own frame of reference, traveling in acircular orbit. That is, if an orbital electron is moving, from left toright for example, synchronously with the high frequencyfield in FIG. 2,then to the electron it will 'appear to be moving in a circle withrespect to that field,

although to a stationary observer the electrons track will describe acycloid. When the cusp of the cycloidal trajectory just grazes thesurface of the sole 2 in FIG. '2, to the electron it will appear thatits circular orbit is tangent to the surface of the negative electrode.Thus, if an electron 11, traveling along a circular orbit is introducedinto the HF. field of FIG. 2 so that the orbit of the electron isrepresented by the circle 12 tangent to the negative electrode 2, ananalysisof the effect of the HF. field on the electron shows that thecircular orbit 12 is lifted upwardly toward the positive electrode andthat the electron 11 does not strike the sole. The electron 11 cor- Theorbit of an unfavorable phased electron 13, for comparison, is

represented by the circle 14 in FIG. 2. An analysis of the effect of theHF. field on the electron 13 shows that its circular orbit is pusheddownwardly so that the electron strikes the negative electrode 2 and isabsorbed. In tubes employing electron sorting, the negative electrodemust not be biased so heavily negative that approaching electrons arerepelled. In tubes employing phase focusing,

kinetic energy in approaching that electrode and therefore strike thenegative electrode with reduced velocity at which time their remainingkinetic energy is transformed into heat energy. For this reason thenegative electrode does not have stringent heat dissipationrequirements. If electrons absorbed by the negative electrode 2 strikethat electrode with sufiicient energy, secondary electrons will beemitted and may interfere with efiective electron sorting. To inhibitsecondary emission, the negative electrode may be coated with a materialhaving low secondary emission characteristics, such as carbon, or thenegative electrode may be fabricated of a material selected for its lowsecondary emission properties. The removal of unfavorable phasedelectrons in an electron stream by the electron sorting mechanismproduces a density modulation of the'stream and the density modulatedstream may then be used in a multitude of applications in theelectronics art.

The discussion of phase focusing and electron sorting, in connectionwith FIGS. 1 and 2, has been limited to the interaction occurringbetween electrons and a traveling wave propagating along a delay line 1polarized positive with respect to the sole 2. There will now beconsidered, with reference to FIG. 3, the phase focusing actionoccurring between electrons and a traveling wave propagating along adelay line 15 polarized negative with respect to a sole electrode 16 andit will become apparent, as the explanation proceeds, that with thisarrangement, the effect of phase focusing is adverse to propitiousmodulation of an electron beam. FIG. 3 illustrates the force lines ofthe high frequency field of a traveling electromagnetic wave propagatingalong the delay line 15, the latter member being negatively polarizedwith respect to the sole. Since a potential difference exists betweendelay line and sole, an electric field E is established which extendsbetween the two members. A constant magnetic field B, at right angles tothe DC. electric field, is established by any suitable means, such as apermanent magnet. As with FIGS. 1 and 2, it is to be understood that toan electron traveling with the same velocity as the phase velocity ofthe traveling wave, the high frequency field appears to be stationary.It will be observed in FIG. 3 that the transverse component E of the HF.field in the regions a and c is in the same direction as the electricfield E and the transverse component E in the region b is oppositelydirected to the field E so that the resultant field E is stronger at aand c and weaker at 11 than the electric field E Consider an electronhaving a rectilinear trajectory, viz, no orbital component of motion,injected at point 17 in FIG. 3 with a velocity equal to the phasevelocity of the traveling wave. Since the transverse HF. field componentE at point 17 reinforces the field E and the electron is accelerated andmoves along the curve 18, perpendicularly to the lines of force, untilthe electron meets and is absorbed by the delay line. An electron atpoint 19 is subject to a decelerating force as the trans verse fieldcomponent E now opposes the field E therefore, the electron at point 19is slowed down and moves along the curve 2% until it is absorbed by thedelay line. Similar analysis shows that an electron at point 21 willmove along the curve 22 until it is absorbed by the delay line. In orderfor electrons to deliver their potential energy to the HF. field theymust move closer to the positive line. In FIG. 3, it is seen, however,that the effect of phase focusing is to cause electrons to be bunched inthe unfavorable phase where they are pushed toward the negativeelectrode. Hence, Where the delay line is polarized negative, the effectof phase focusing is adverse to the transfer of energy from an electronbeam to the high frequency field. More than this, the effect of phasefocusing tends to cause absorption of the electron beam by thenegatively polarized delay line.

The electron sorting action which occurs with a negatively polarizeddelay line is diagrammatically shown in FIG. 4 which depicts the samedelay line, sole, electric, magnetic, and high frequency fieldsillustrated in FIG. 3. Consider first an electron, having an orbitalmotion, situated in the favorable phase of the HF. field. Such anelectron is the electron 23 moving in the circular orbit 24. The effectof the favorable phase of the HR field is to push the electron 24-upward toward the positive polarized sole 16 so that the electron at itsnadir does not strike the delay line and as time progresses the averageposition of electron 24 gradually approaches closer to the sole wherebyenergy is delivered by the electron to the HF. field. Since the H.F.field is strongest adjacent the negatively polarized delay line andweakest adjacent the sole and because the average position of electronsinjected into the field is close to the delay line, a strong initialinteraction is achieved between electrons and the HP. field. Of course,the interaction grows weaker as the favorably phased electrons movecloser to the positive electrode 15. An electron 26, situated in theunfavorable phase of the HF. field, is shown in FIG. 4 traveling in thecircular orbit 27. The efiect of the unfavorable phase of the field isto pull the electron 26 downwardly toward the delay line 15 so that atsome point in its orbit the electron strikes the delay line and isabsorbed. The electron sorting mechanism removes from an electron beamelectrons in the unfavorable phase by causing their absorp- .tion in thenegative electrode, and the remaining electrons are predominantly in thefavorable phase so that the electron beam is, in effect, densitymodulated. It is seen, therefore, that with a negatively polarized delayline, the effect of phase focusing adversely affects the desiredbunching of electrons in the beam, whereas electron sorting produceselectron bunches which are in the desired phase of the high frequencyfield. By injecting electrons which have an orbital component of motioninto the H.F. field, the mechanism of electron sorting is made topredominate over the adverse phase focusing effect and the desireddensity modulation of the electron beam is attained. It is noteworthythat space charge effects tend to aid the electron sorting actionbecause electron bunches, by virtue of space charge effects, tend tocongregate into spherical charges and thus electron bunches, onceformed, tend to form coherent electron aggregates which resist thedisintegrative phase focusing force.

The mechanism of electron sorting has thus far been described withreference to an electromagnetic wave propagating along a delay line. Thedelay line may be replaced by a density modulated electron beam as awave circuit element since it is known that a density modulated electronbeam does support a high frequency field. Thus, in FIG. 5 an electricfield E is established between two parallel plates, the upper plate 28being polarized positive with respect to the lower plate 29 byimpressing a potential between the two plates. A magnetic field B isestablished transversely to the DC. electric field. In lieu of a delayline, a modulated electron beam 30 is caused to flow between the twoplates, the electron beam being positioned adjacent the positivelypolarized plate 28. A stream of electrons, in which the electrons havean orbital component of motion, is introduced into the crossed fields sothat in the absence of a high frequency field the electrons follow thearcuate trajectory 31 which lies adjacent to the negative plate 29.Since the electron beam 34) is density modulated, it sustains a highfrequency field which influences the orbital electrons to cause thoseelectrons in the unfavorable phase to be pushed downwardly onto thenegative electrode and those electrons in the favorable phase to bepulled upwardly and follow the arcuate path 32. Now, it is known that anenergy transfer between two beams of charged particles may be made tooccur if at least one of the beams carries a density or velocitymodulation. This energy transfer between the beam following the path 32and the density modulated beam 30 causes an amplification of the spacecharge variation in beam 30 and hence an intensification of the highfrequency field which in turn enhances the effectiveness of the electronsorting action. Thus, once an effective transfer of energy from the beam32 to the beam 30 occurs the interaction tends to becomeself-perpetuating, inasmuch as better electron sorting permits moreenergy to be transferred to the HF. field. While the beam 30 wasdescribed as being initially density modulated, it should be understoodthat an unmodulated electron beam contains sufficient density variationsso that a weak high frequency field accompanies the unmodulated beam.For this reason, electron sorting will occur in the apparatus of FIG. 5even though the beam 30 is initially unmodulated. Once electron sortingcommences, the m teraction between the two beams will rapidly build upto permit a considerable amount of energy to be transferred to beam 30.By this means two density modulated beams are produced. The ultimateutilization of one or the other or both of the modulated beams will, ofcourse, depend upon whatever apparatus employs the beam sorting device.

An elemental form of the invention is schematically illustrated in FIG.6 which depicts the internal elements of a traveling wave tube of theM-type and the potentials which are applied to such elements. Anelectron gun, here indicated by a cathode 41 and an acceleratingelectrode 42, is positioned at one end of the tube and a collectorelectrode 43 is disposed at the opposite end. A delay line 44 is spacedfrom a sole electrode 45 and a DC. source of electric potential,represented by the battery 46, is connected to cause the delay line tobe polarized negatively with respect to the sole, thereby establishingan electric field E between those two members. A constant magnetic fieldB is established transversely to the electric field E so that thecombined effect of the crossed fields causes electrons subject to thecrossed fields to travel from the gun toward the collector. The electrongun is constructed to cause electrons ejected from the gun to have anorbital component of motion and the electrons, therefore, follow anarcuate trajectory, since the electrons are moving in an orbit whilesimultaneously being translated under the action of the crossed fields.In the absence of any other fields, an electron, once ejected from thegun along an arcuate path, continues to maintain an arcuate path, asindicated by the broken line 47. However, a wave propagating along delayline 44 has associated with it a H.F. field which tends to moveelectrons away from or toward the delay line, depending on the phase ofthe electrons with respect to the HF. field. Thus, if wave energy ispresent on the delay line, some of the electrons traveling along thearcuate path 47 are driven into the negatively polarized delay line 47and are absorbed upon contact with that member whereas other electronsare raised toward the posi tively polarized sole 42 and continue tointeract with HF. field of the traveling wave. Electrons whichcompletely traverse the interaction space between delay line and soleare absorbed by collector electrode 43 which is maintained at apotential below the potential impressed on the sole 45. If desired, thecollector electrode need not be an independent element but may be anextension of the sole 45. However, by employing an independent collectorelectrode the beam can be collected at a lower voltage therebydecreasing the heat which must be dissipated by the tube. Assuming thatthe tube of FIG. 6 is utilized as an oscillation generator, and thatdelay line 44 is constructed to have a backward wave fundamental, anoutput signal is derived from an output coupling 48 located at the endof the delay line adjacent the electron gun. Moreover, as the H.F. fieldassociated with a backward wave delay line is most intense adjacent theelectron gun end and least intense adjacent the collector end, theintense H.F. field at the gun end of the delay line causes immediate andpotent electron sorting of the beam emanating from the electron gun. Itis to be understood that when an electron beam is initially injectedinto the interaction space, noise components in the beam induce waves onthe delay line so that a HP. field is always present whenever a beam ispresent to cause beam sorting to be initiated in an oscillator tube. Anosc1l lator tube having a negatively polarized delay line is advantageous inasmuch as the electron beam is injected along an arcuatepath lying adjacent to the delay l ne, thereby permitting the electronsto interact with the untially weak field which exists close to the delayline at the outset before oscillations have built up to appreciablestrength.

Where the tube shown in FIG. 6 includes a delay line having a backwardwave fundamental and is to be employed as an amplifier, an input signalis impressed on the delay line 44 through the input coupling 49 so thata high frequency field of appreciable strength is present in theinteraction space. In this circumstance the arcuate path of the electronbeam may be spaced somewhat farther from the delay line than is the casein an oscillator tube since the high frequency field of the wave presenton the delay line in an amplifier can influence electrons at appreciabledistances from the delay line and effectuate electron sorting.

Referring now to FIG. 7 of the drawings, which represents indiagrammatic form a crossed field traveling wave tube employing electronsorting, there is shown a delay line 50, constructed to have either abackward wave or forward wave fundamental, spaced from an elongatedelectrode 51, known as the sole, and a sorting electrode 52 which ispreferably coplanar with the sole, although this disposition is notessential. An electron gun, here indicated by a cathode 53A, a gridstructure 533 and an accelerating electrode 53C, acts as an electronsource and a collector electrode 54 is positioned at one end of the tubeto absorb those electrons which completely traverse the interactionregion. It is to be understood that the aforementioned structure'iscontained within an evacuated envelope, not illustrated, provided withthe necessary leads for establishing electrical connections with theinternal elements. An unvarying magnetic field B is establishedthroughout the tube by any suitable means, such as a permanent magnet oran electromagnet. The symbol signifies that the magnetic field isdirected into the plane by the drawing. A DC. electric field isestablished between the delay line 50 and the sole 51 by the voltagesource 55 so that the polarity of the delay line is positive withrespect to the sole. By means of a variable voltage source 56 thesorting electrode 52 may be made more positive or more negative withrespect to the cathode 53A. The delay line is provided with couplings 57and 58 at either end by means of which input signals may be impressedand H.F. energy extracted. If the tube is employed as an autooscillator, only an output coupling need be provided and the frequencyof oscillation may be changed by varying the voltage between the delayline and the sole. In a backward wave oscillator the output couplingwould be located adjacent the gun end of the tube, whereas in a forwardwave oscillator the output coupling may be located at either end. Wherethe tube is employed as a backward wave amplifier, input signals arecoupled into the tube at 58 and the output taken from coupling 57. Ifthe tube is a forward wave amplifier the output is taken at 58 and theinput signal inserted at 57. The optics of the electron gun causeselectrons emitted from the cathode 53A to have an orbital component ofmotion, and the electrons therefore follow a generally cycloidal path69A which path may be adjusted by the variable voltage source 56 tocause the electrons to graze the negatively polarized sorting electrode52 at the collection point 59. .Assuming that H.F. wave energy istraveling along the delay line 50, the associated H.F. field can beresolved into a longitudinal component B and a transverse component E aspreviously de scribed in connection with FIG. 2. Electrons entering thesorting region which encounter a positive longitudinal component E ofthe H.F. field are caused to be defiected upwardly toward the delay lineand do not strike the negative electrode; those electrons whichencounter a negative longitudinal component E are deflected downwardlyand are absorbed by the sorting electrode 52. Thus, there takes place inthe sorting region an absorption of electrons which are in anunfavorable phase with respect to the HP. field so that most of theelectrons which leave the sorting region enter the interaction region inthe favorable phase of the HP. field. Since the unfavorable phase of theHF. field has associated with it less electrons than the favorablephase, the beam can be considered as consisting of bunches of electrons.In

its simplest aspect, this sorting process is the result of the movementof individual electrons perpendicular to the HF. field of the delay lineand the magnetic field B. It should be understood that the initialtrajectory of the electrons need not be cycloidal but may follow anyarcuate path which will just graze or closely approach the sortingelectrode 52. When the bunched electron beam enters the interactionspace, it will continue to follow a generally cycloidal path unless aperturbation is introduced to change the beams trajectory. For the mostefiicient operation, it is necessary that the electron beam follow arectilinear path in the interaction region. The traveling wave tube is,therefore, provided with means to perturb the beam to cause the beam tofollow a rectilinear path. The perturbation is caused, as hereillustrated, by an electrode 62, termed a phasing electrode, which issituated between, and insulated from, the sole 51 and sorting electrode52. By establishing an electric field between the phasing electrode andthe delay line, a perturbation is introduced which, if properlyadjusted, will cause the trajectory of the electron beam to be changedfrom a cycloidal to a more rectilinear path. To

those familiar with electron optics, it is manifest that the desiredperturbation may optionally be achieved by locally distorting themagnetic field in the tube at appropriate locations. In FIG. 7 theelectrons spend approximately one half of the period of a cycloid in thesorting region so that there is only one electron collection point,indicated at 59. The sorting region can be extended, if desired, topermit the electrons to remain in that region for a longer period oftime for more effective initial modulation of the beam. Thus, the regionmay be extended to provide two or more collection points so that thefavorably phased electrons describe three halves or more of a cycloid intraversing the sorting region. As the beam enters the interactionregion, the trajectory of the electrons is changed from a cycloidal to arectilinear path, by the phasing electrode 62. By means of the phasingelectrode, a phase shift may be introduced between the electron bunchesin the beam and the RF. field. The phasing electrode is convenient,since, if the sorting action does not bunch the electrons at exactly thefavorable phase of the HF. field, the phase of the electron bunches canbe corrected. The required location of the phasing electrode variesaccording to the intended application of such a system. The phasingelectrode is maintained, by the variable voltage source 61, at a DC.voltage which alters the relative phase between the electrons in thebeam and the interacting space component of the Wave traveling along thedelay line, the sense depending on whether there exists in the phasingregion the first or second half of the cycloid period of the electrontrajectory. The electron beam formed in the sorting region proceedsthrough the perturbation region and thence into the interaction regionwhere the modulated beam transfers energy to the wave traveling alongthe delay line. The electrons in the interaction region deliver theirpo' tential energy to the high frequency field and, in doing so, movecloser to the positively polarized electrode 50. The predominant numberof electrons in the interaction region follow a path exemplified by thetrajectory 60B and are absorbed by the collector electrode 54 Anappreciable number of electrons in the interaction region, however,deliver all of their potential energy and strike the delay line 56,whereupon the kinetic energy of the impinging electrons is transformedinto heat energy. The heat energy which is required to be dissipated bythe delay line is related to the output power delivered by the tube,and, because a delay line cannot easily be cooled, the heat dissipatingcapabilities of the delay line impose a limitation upon the maximumpower obtained from such a tube.

The construction of the traveling wave tube depicted in FIG. 7 permitsthe tube to be pulsed merely by varying the potential of the voltagesource 56. It can be appreciated that if the sorting electrode, 52is'made sufficiently positive with respect to the cathode 53A of theelectron gun, all the electrons emanating from the gun will be attractedtoward the sole and the entire electron beam will be absorbed in thesorting electrode. Hence, by varying the voltage of source 56, the tubecan be pulsed on and off. If the tube is employed as an oscillator, itsfrequency of oscillation may be changed by adjusting the voltageimpressed by battery 55 between delay line 56 and sole 51. The amplitudeof the oscillations may be modulated by adjusting the voltage impressedby battery 56 between sort ing electrode 52 and the cathode of theelectron gun, since the potential of the sorting electrode with respectto the cathode 53A determines the proportion of the beam which isabsorbed. Thus, frequency modulation and amplitude modulation areeffected in the tube by simply varying the voltages supplied by sources55 and 56. As is well known, the frequency of a backward wave oscillatormay be continuously varied over an extremely wide frequency range and,of course, the delay line 50 shown in FIG. 7 may be of the backward wavetype. v

FIG. 8 illustrates an embodiment of the invention employing electronsorting in a traveling wave tube having a delay line 63 negativelypolarized with respect to the sole 64 by means of a battery 65. It is tobe understood that delay line 63 may be constructed to have either aforward or backward fundamental wave component. By suitable .means, suchas an electromagnet or a permanent magnet,

an unvarying magnetic field B is established in the tube transversely tothe electric field existing between the delay line 63 and sole 64. Anelectron gun, represented by a cathode 66, a grid '77, and anaccelerating electron 67, is designed to cause electrons having anorbital component of motion to follow an arcuate path 68 into thesorting region. If the tube is to be employed as an oscillator the cuspof the arcuate path preferably grazes the surface of the delay line atthe collection point 69. The sorting region, in this illustration, isextended so that the electrons in the unfavorable phase may also becollected at a second point 70 which is spaced from the first collectionpoint by one cycloidal period. The HP. field in the sorting regioncauses electrons in the favorable phase to be deflected upwardly andelectrons in the unfavorable phase to be deflected downwardly, aspreviously explained in connection with FIG. 4. Electrons which aredeflected downwardly in the sorting region are removed from the electronbeam upon striking the delay line 63 and being absorbed by that member.In order to inhibit secondary emission, the delay line in the sortingregion is coated with carbon or some other suitable material which haslow secondary emissivity. After transit of the sorting region, theelectrons remaining in the beam enter a perturbation region where thebeam is acted on by a perturbation field established by the phasingelectrode 71, whereby the beam is thenceforth caused to follow arectilinear path to the collector electrode 72. The phasing electrode 71is situated in, but insulated from the positive sole electrode 64. Inestablishing an electric field between the phasing electrode and thesole 64 by means of a variable voltage source 73, a perturbation isintroduced which causes the trajectory of the electron beam to bechanged from an arcuate to a more rectilinear path. The electron beampasses through the perturbation region into the interaction region wherethe density modulated electron beam trans fers energy to the wavetraveling along the delay line. As the electrons in the beam deliverenergy to the traveling wave, the electrons move closer to the positiveelectrode 64 since it is the potential energy of the electrons which istransferred to the wave. The majority of electrons in the interactionregion, therefore, follow a path exemplified by the trajectory 74 andare absorbed by the collector electrode 72 which is maintained at apotential less positive than the potential on the sole to reduce theheat generated by the impinging beam. Notall the electrons in theinteraction region are absorbed by the collector elec- 1 I trade sincean appreciable number of electrons in the interaction region deliver alltheir potential energy and strike the positive electrode 64. The kineticenergy of electrons striking sole 64 is turned into heat energy whichmust be dissipated by the positive electrode if the tube is not to bedamaged. Since the sole essentially is a flat plate, it is readilycooled by circulating a coolant fluid through channels in the plate. Adelay line, on the other hand, is a more complex structure and cannot beso readily cooled. As a matter of interest, the power developed by atraveling wave tube of the type shown in FIG. 7 is largely limited bythe heat which must be dissipated by the delay line 50. It has beenexperimentally found that the power required to be dissipated in heat bya positively polarized delay line (FIG. 7) is in the order of one tothree times as great as the output power derived from the tube, whereasthe power required to be dissipated as heat by a negatively polarizeddelay line (FIG. 8) is in the order of one tenth to three tenths of theoutput power of the tube. Therefore, for tubes having comparable poweroutput, the heat dissipated by a delay line in a tube of the type shownin FIG. 8 is in the order of ten times less than the heat dissipated bya delay line in a tube of the type shown in FIG. 7. Because of thisgmcumstance, traveling wave tubes having a negatively polarized delayline of the type portrayed in FIGS. 6 and 8 can be constructed todeliver amounts of output power which are quite beyond the ability ofcomparable traveling waveemployed, depending upon the construction ofthe delay line 63, as a forward Wave amplifier, forward Wave oscillator,backward wave amplifier, or backward wave oscillator. Where the tube isused as a forward wave amplifier or oscillator, the delay line isconstructed to have a fundamental wave component which travels in thesame direction as the electron beam. The output from a forward wave tubeis extracted through the coupling 75 extending from the delay lineadjacent the collector end of the tube and signal energy is introducedinto the tube through the coupling 76 secured to the delay line adjacentthe gun end of the tube. Where the tube is used as a backward-waveamplifier or oscillator the delay line 63 is constructed so that thefundamental component of a wave propagates along the delay line in adirection opposite to the direction of the electron beam. The output ofa backward wave tube is derived through the coupling 76 and inputsignals are coupled into the tube at 75'.

While the embodiments of the invention shown in FIGS. 6, 7 and 8 areillustrated in the form of linear tubes, it is entirely feasible toembody. the invention in tubes of circular form. A circular tube, inessence, is simply a linear tube, such as is shown in FIGS. 6, 7 and 8,which has been bent into a circle. For example, FIG. 9 depicts acircular tube which is essentially the same as the tube con-.

taining a negatively polarized delay line. It will be observed thatwithin the envelope 80 of the circular tube there is contained a delayline 81, preferably of the interdigital type and constructed to have abackward fundamental Wave component, a sole electrode 82. concentricwith the delay line, a phasing electrode 83 situated in and insulatedfrom the sole electrode, a collector electrode 86, and an electron gunrepresented by a cathode 84, a grid 88 and an accelerating electrode 85.It is to be understood that the potentials applied to these internalelements are similar to the potentials applied to the tube elemens ofFIG. 8. It will be observed that the delay line 81 of the circular tubeis concentric with the sole 82 and that the sole is internally situatedwith regard to the delay line. The delay line 81 is mechanicallyattached to the metallic tube envelope 8% and, therefore, for reasons ofsafety, it is desired that the delay line and tube envelope bemaintained at ground potential. Since the delay line 81 is polarizednegatively with respect to the sole, a high positive voltage is requiredto be impressed on the sole. By locating the positively polarizedelectrode 82 in the interior of the circular tube, an advantage isderived in that a somewhat weaker magnetic field B is required than isthe case where the negative and positive electrodes in the circular tubeare reversed in position. The reason for this is that the average speedof electrons in the beam is equal to the ratio where E is the intensityof the DC. electric field and B represents the intensity of the magneticfield. The elec tric force acting on the electrons is balanced by theLorentz force due to the speed of electrons and to the magnetic field.The centrifugal force exerted on an electron moving along the circularpath 87 tends to aid the Lorentz force exerted on the electron by themagnetic field B so that the magnetic field intensity B can be reducedin intensity by an amount which offsets the centrifugal force. Thesignificance of this is that a smaller magnet may be used to supply therequired magnetic field intensity.

FIG. 10 schematically depicts a species of traveling wave tube employingelectron sorting in which two oppositely polarized delay lines areutilized. An electric field is established between the positivelypolarized delay line 99 and the negatively polarized delay line 91 bysuitable connections to a voltage source, here represented by thebattery 92. A magnetic field B is established transversely to theelectric field by any suitable means, such as an electromagnet. Anelectron gun comprising a cathode 93, grid 94, and acceleratingelectrode 95 is designed to inject electrons having an orbital componentof motion into the crossed field region whereby the electrons follow anarcu ate path, such as the path 96. At the end of the tube opposite theelectron gun end, there is disposed a collector electrode 97 whichabsorbs the electron beam after it traverses the interaction regionbetween the two delay lines. The two delay lines may be constructed tohave either a forward or a backward fundamental wave component. Now awave traveling along one of the delay lines 99 or 91 will induce a waveon the other delay line. By appropriate design of the delay lines, theHF. fields of the two waves may be phased so as to enhance theinterchange of energy between the electron beam and V the travelingWaves. Since two complementary H.F. fields are present in theinteraction region, one high frequency field being associated with thetraveling wave on delay line and the other HF. field being associatedwith the traveling wave on delay line 91, effective electron sorting ofelectrons emanating from the electron gun is achieved. Electrons whichare favorably phased will form a density modulated beam and the beamwill gradually approach closer to the positive delay line 90 along thepath 98, for example, while delivering its energy to the travelingwaves. High frequency energy may be extracted from the tube by couplingto either or both of the delay lines. For example, if the tube isutilized as a backward wave oscillator, energy may be extracted from thetube through the coupling 99 associated with the delay line 90, throughthe coupling 100 associated with the delay line 91, or through bothcouplings. As a corollary, if the tube is utilized as a backward waveamplifier, input signals may be impressed on either of the couplings 101and 102 or on both couplings. Where the tube is utilized as a forwardwave oscillator, energy may be extracted from the tube at any of thecouplings 99, 100, 101 and 1M. Where the tube is utilized as a forwardwave amplifier the input and output terminals are they reverse of thosein a backward wave amplifier.

FIG. 11 schematically illustrates an improvement upon the tube shown inFIG. 10. As shown in FIG. 11, an

electric field is established between the positively polarized delayline 165 and the negatively polarized delay line 106 by connecting thosemembers to a source of electric potential, such as the battery 1W.Transversely to the electric field there is established a magnetic fieldby any suitable means, such as a permanent magnet. A sorting electrode1&8 and a phasing electrode lit-9 are preferably coplanar with thenegative delay 1%. An electron gun, represented by a cathode 116, a grid11:1, and an accelerating electrode 112, is arranged to cause electronsemitted from the cathode to have an orbital component or" motion and toinject such electrons along an arcuate path into the sorting regionwhere the electrons are subjected to the high frequency field of a wavepropagating along delay line 105. As explained in connection with PEG.2, electron sorting occurs so that the unfavorably phased electrons areabsorbed by the nega tive electrode, which in the case of the tube shownin FIG. 11, is the sorting electrode 108. By means of the adjustablevoltage source 113, the potential of the sorting electrode with respectto the potential of the cathode 116 may be changed to obtain the optimumcondition for electron sorting. The sorting electrode may also beemployed for any of the purposes set forth in discussing the sortingelectrode in the embodiment of FIG. 7, that is, for pulsing or amplitudemodulating the output of the tube. After electron sorting of the beamhas occurred, the beam in FIG. 11 enters a perturbation region where thebeam is caused to change its trajectory to a more linear path,exemplified by the path 114. The beam then enters the interaction regionWhere electrons deliver up their potential energy and are absorbed bythe collector electrode 115. As previously explained in connection withFIG. 10, a wave traveling along one of the delay lines induces a wave onthe other delay line. Thus a wave traveling along delay line N in FIG.11 induces a wave which propagates along delay line 1%. It will be notedthat energy is extracted from the tube by means of a coupling 116 or 117situated at the ends of the positively polarized delay line 105. Ifdelay line 105 is of the forward wave type, energy may be extracted fromeither coupling, whereas if the delay line is of the backward wave type,energy is extracted from coupling 116. The ends of delay line 106 areappropriately terminated to obtain maximum power output from the tubewhich is consistent with the desired frequency range.

FIG. 12 illustrates electron sorting as it applies to a type oftraveling wave tube known as a linear torotron and shows a verticalsection through the tube. The delay line 11% of such a tube may, by wayof example, be comprised by a metallic cylinder 12!} having annulardiscs 121 extending inwardly to form a disc loaded waveguide. Disposedalong the longitudinal axis of the cylindrical delay line is a soleelectrode 122 which may be simply a metallic rod capable ofaccommodating the flow of a very high current furnished from thesecondary of the transformer 123, for example. An electron gun 124,represented by an annular cathode 125 and an annular acceleratingelectrode 126, is disposed at one end of the delay line and a collectorelectrode 127 is arranged at the opposite end. A radial electric fieldis established between delay line 119 and sole 122 by suitableconnections to the voltage source 128 such that the delay line ispositively polarized and the sole is negatively polarized. In order toestablish a magnetic field transversely to the radial electric field, ahigh current is caused to fiow in the sole by the transformer 123. Whenthe current flow is in the appropriate direction, the crossed electricand magnetic fields cause electrons to be propelled from the electrongun end of the delay line toward the collector electrode 427. Electrongun 124 is constructed to form a hollow cylindrical beam of electrons inwhich the electrons have an orbital component of motion. The hollowcylindrical bearn,'therefore, in effect, constricts and enlarges itsdiameter as the electrons flow through the region between the sole 122and delay line 119. Due to the effect of the HF. field associated withan electromagnetic wave propagating along delay line 119, electronsorting occurs which causes a density modulation of the hollowcylindrical beam. Electrons which are in the unfavorable phase are drawnradially inward toward the negatively polarized sole 122 and areabsorbed, whereas electrons in the favorable phase are pushed radiallyoutward toward the delay line 119 and continue to travel towardcollector electrode 127 in synchronism with a component of theelectromagnetic wave propagating along the delay line. It should benoted that tubes of this type are usually operated by pulsing as veryhigh currents are required to be driven through the sole 122 in order toestablish the necessary magnetic field in the interaction space. Highcurrents cause rapid heating of the sole so that continuous operation ofsuch a tube is not feasible unless the sole can dissipate the generatedheat. This implies some means of cooling the sole, such as bycirculating a coolant through the center of that electrode. In itssimplest aspect, the toroidal tube of FIG. 12 is analogous to a tube ofthe type shown in FIG. 6 which has been rotated about a longitudinalaxis.

Electron sorting devices have been illustrated herein as incorporated invarious types of crossed field tubes, but it should be understood thatthese illustrations are exemplars only, and that electron sortingdevices may be employed in other types of tubes such as injectionmagnetrons, for example.

This completes the description of the embodiment of the inventionillustrated herein. However, modifications and advantages thereof willbe apparent to persons skilled in the art without departing from thespirit and scope of this invention. Accordingly, it is desired that thisinvention not be limited to the particular details of the embodimentdisclosed herein except as defined by the appended claims.

What is claimed is:

1. An electronic device comprising a source of electrons, delay meansfor guiding an electromagnetic wave whereby a high frequency field isestablished in a region of said device bounded by said delay means,means for injecting electrons from said source into said region, meansproducing steady transverse magnetic and electric fields in said regionimparting an orbital component of motion to said electrons and causingsaid injected electrons to travel in synchronism with the phase velocityof a component of said wave, and means for causing a substantial portionof said injected electrons which are in unfavorable phase with respectto said high frequency fields to be removed from said region duringmovement of said injected electrons within said region.

2. An electron sorting device comprising a source of electrons, meansfor establishing an electric field in a region of said device, means forestablishing a magnetic field in said region transverse to said electricfield, means in said region for guiding and retarding the propagation ofa wave along said region, means for injecting electrons from said sourceinto said region whereby said transverse fields impart an orbitalcomponent of motion to said electrons and cause said electrons to travelat a velocity equal to the velocity of a component of said wave, saidmeans for establishing an electric field including an electricallypolarized element situated adjacent the initial path of said injectedelectrons, and means including said polarized element for causing asubstantial portion of the injected electrons which are in unfavorablephase with respect to said high frequency fields to be absorbed by saidelement.

3. An electron sorting device comprising a source of electrons having anorbital component of motion, a pair of spaced electrodes, at least oneelectrode of said pair comprising a wave retardation line, means forestablishing an electric field between said electrodes, means forestablishing a magnetic field transverse to said electric field, meansfor injecting electrons from said source into the crossed electric andmagnetic fields whereby said electrons are caused to have an orbitalcomponent of motion and travel synchronously with a component of a wavepropagating along said retardation line, and one of said electrodesbeing situated adjacent the path of injected electrons and maintained ata potential suitable for allowing absorption of a substantial portion ofsaid injected electrons which are in unfavorable phase with respect tosaid high frequency fields, said electron phase being determined by saidorbital component of motion.

4. An electron sorting device comprising a source of electrons, meansincluding a delay line for establishing an electric field in a region ofsaid device, means for establishing a magnetic field in said regiontransverse to said electric field, means for injecting electrons fromsaid source into said region whereby said transverse fields impart anorbital component of motion to saidinjected electrons and cause saidelectrons to travel synchronously with a component of an electromagneticwave propagating along said delay line, and said means for establishingan electric field including an element situated adjacent the initialpath of said injected electrons, said element being maintained at apotential suitable for absorption of a considerable portion of saidinjected electrons which are in unfavorable phase with respect to saidhigh frequency fields.

5. An electron sorting device comprising a source of electrons having anorbital component of motion, a pair of spaced delay lines, means forelectrically polarizing one of said delay lines negative with respect tothe other delay line of said pair to establish an electric field, meansfor establishing a magnetic field transverse to said electric field,means for injecting electrons at least some of which have an orbitalcomponent into the crossed electric and magnetic fields whereby saidelectrons are caused to have an orbital component of motion and travelsynchronously 'with a component of a wave propagating along said delayline, and said one delay line being receptive of a substantial portionof said injected electrons which are in unfavorable phase with respectto said high frequency fields, said electron phase being determined bysaid orbital component of motion.

6. A traveling wave interaction device comprising a delay line, anelongate member spaced from said delay line, said delay line and membercomprising a pair of electrodes defining a single continuous interactionspace, means for electrically polarizing said delay line negative withrespect to said elongate member to establish an electric fieldtherebetween, means for establishing a magnetic field transverse to saidelectric field, means forinjecting electrons into the crossed electricand magnetic fields to have an orbital component of motion and causesaid electrons to travel synchronously with a component of a wavepropagating along said delay line, the negatively polarized one of saidelectrodes extending adjacent the initial path of injected electrons andmaintained at a potential permitting absorption of'asubstantial portionof said orbital electrons which are in'unfavorable phase with respect tosaid high frequency fields, said electron phase being determined by saidorbital component of motion whereby a density modulated beam ofelectrons is produced, and a collector electrode positioned to interceptsaid modulated beam.

7. A traveling wave interaction device comprising a single continuousdelay line for guiding an electromagnetic wave whereby a high frequencyfield is established in a region bounded by said delay line, an elongatesole electrode spaced from said relay line and bounding therewith aninteraction region, a sorting electrode spaced from said delay line andbounding therewith a sorting region, means for establishing an electricfield in each of said regions, means for establishing a magnetic fieldtransverse to the electric field in each of said regions, and means forinjecting electrons into said sorting region 16 whereby said transversefields impart an orbital component of motion to said electrons andcompel said electrons to move in energy-imparting relation with saidhigh frequency field throughout said interaction and sorting regions.

8. A traveling wave interaction device comprising a first delay line, asecond delay line spaced from said first delay line and boundingtherewith an interaction region, said delay lines guiding anelectromagnetic wave whereby a high frequency field is established in aregion bounded by said delay line, a sorting electrode spaced from saidsaid first delay line and bounding therewith a sorting region, means forestablishing an electric field in each of said regions, means forestablishing a magnetic field transverse to the electric field in eachregion, and means for injecting electrons into said sorting regionwhereby said transverse fields impart an orbital component of motion tosaid electrons and compel said electrons to move along a pathapproaching said sorting electrode and in energy-imparting relation withsaid high frequency field throughout said interaction and sortingregions.

9. A traveling wave interaction device comprising a delay line, anelongate member spaced from said delay line and bounding therewith aninteraction region, a perturbation means spaced from said delay line anddisposed adjacent a portion of said elongate member, means forestablishing an electric field in each of said regions, means forestablishing a magnetic field transverse to said electric field in eachof said regions, means for injecting electrons into said sorting regionwhereby said transverse fields impart an orbital component of motion tosaid electrons and compel said electrons to move through saidinteraction region along an arcuate path approaching said elongatemember, a substantial portion of said electrons approaching saidelongate member being absorbed by said member, said perturbation meanscausing electrons traversing said interaction region to alter theirarcuate trajectories to a more linear path, and a collector electrodepositioned to intercept electrons which completely traverse saidinteraction region.

10. A traveling wave tube comprising a delay line, an elongated soleelectrode spaced from said delay line and including therebetween anelectron sorting region and an interaction region, means forestablishing an electric field between said delay line and said sole,means for establishing a magnetic field transverse to said electricfield, an electron gun positioned adjacent said sorting region, theoptics of said electron gun causing electrons emitted fromsaid gun tohave an orbital component of motion whereby said electrons follow anarcuate trajectory into said sorting region, perturbation means forestablishing a perturbation region between said sorting region and saidinteraction region, said perturbation means causing electrons traversingsaid sorting region to alter their arcuate trajectories to a more linearpath, and a collector electrode situated adjacent the end of saidinteraction region for intercepting electrons which completely traversesaid interaction region.

11. A traveling wave tube comprising a delay line, an elongated soleelectrode spaced from said delay line and including therebetween asorting region separated from an interaction region by a perturbationregion, means applying an electric potential between said delay line andsaid sole for establishing an electric field and causing said delay lineto be polarized negative relative 'to said sole, an electron gunpositioned adjacent said sorting region, said electron gun having opticscausing electrons emitted therefrom to follow an arcuate path into saidsorting region which path intercepts said delay line in the absence ofradio-frequency energy on said delay line, perturbation means, saidperturbation means causing the electrons traversing said sorting regionto alter their arcaute trajectories to a susbtantially rectilinear path,a collector electrode situated at the end of said interaction space forabsorbing electrons which com- 17 pletely traverse said interactionregion, and means for establishing a magnetic fieldin said tube normalto said electric field whereby electrons are urged from said gun towardsaid collector electrode.

12. A traveling wave tube comprising a delay line constructed to causethe phase velocity of the fundamental wave to be directed inversely tothe direction of group velocity, an elongated sole electrode spaced fromsaid delay line and including therebetween a sorting region separatedfrom an interaction region by a perturbation region, means applying anelectric potential between said delay line and said sole forestablishing an electric field and causing said delay line to bepolarized negative relative to said sole, an electron gun positionedadjacent said sorting region, said electron gun having optics causingelectrons emitted therefrom to follow an arcuate path into said sortingregion which path closely approaches the surface of said delay line inthe absence of radiofrequency energy thereon, a phasing electrodelocated in said perturbation region adjacent said sole, means forapplying an electric potential to said phasing electrode, a collectorelectrode situated at the end of said interaction spac for absorbingelectrons which completely traverse said interaction region, and meansfor establishing a mag netic field in said tube normal to said electricfield whereby electrons are urged from said gun toward said collectorelectrode.

13. A traveling wave interaction device comprising a source forproviding electrons having an orbital component of motion, an arcuatedelay line, an arcuate sole electrode spaced from and concentricallydisposed within the arc formed by said delay line, means forelectrically polarizing said delay line negative with respect to saidsole to establish an electric field therebetween, means for establishinga magnetic field transverse to said electric field, means for injectingorbital electrons into the crossed electric and magnetic fields to causesaid electrons to travel in the region between said delay line and saidsole, said delay line extending adjacent the initial path of injectedelectrons, said delay line polarization permitting absorption of asubstantial portion of the orbital electrons whereby a density modulatedbeam of electrons is produced, and a collector electrode positioned tointercept said modulated beam.

14. A traveling wave interaction device comprising a delay line, anelongate electrode spaced from and surrounded by said delay line, meansfor establishing an electric field between said delay line and saidelectrode whereby said electrode is negatively polarized with respect tosaid delay line, means for establishing a magnetic field transverse tosaid electric field, and means for injecting electrons having an orbitalcomponent of motion into the crossed electric and magnetic fieldswhereby some of said electrons follow a path approaching said negativelypolarized electrode, said polarization permitting absorption of asubstantial portion of those electrons approaching said negativelypolarized electrodes by said electrode.

References Cited in the file of this patent UNITED STATES PATENTS2,295,315' Wolfii Sept. 8, 1942 2,687,777 Warnecke et a1. Aug. 31, 19542,702,370 Lerbs Feb. 15, 1955 2,861,212 Lerbs Nov. 18, 1958 2,880,353Warnecke et al Mar. 31, 1959 2,976,455 Birdsall et a1. Mar. 21, 196-12,992,360 Reviden July 11, 1961 FOREIGN PATENTS 209,957 Australia Aug.8, 1957 1,141,687 France Mar. 18, 1957 712,565 Great Britain July 28,1954 733,349 Great Britain July 13, 1955

1. AN ELECTRONIC DEVICE COMPRISING A SOURCE OF ELECTRONS, DELAY MEANSFOR GUIDING AN ELECTROMAGNETIC WAVE WHEREBY A HIGH FREQUENCY FIELD ISESTABLISHED IN A REGION OF SAID DEVICE BOUNDED BY SAID DELAY MEANS,MEANS FOR INJECTING ELECTRONS FROM SAID SOURCE INTO SAID REGION, MEANSPRODUCING STEADY TRANSVERSE MAGNETIC AND ELECTRIC FIELDS IN SAID REGIONIMPARTING AN ORBITAL COMPONENT OF MOTION TO SAID ELECTRONS AND CAUSINGSAID INJECTED ELECTRONS TO TRAVEL IN SYNCHRONISM WITH THE PHASE VELOCITYOF A COMPONENT OF SAID WAVE, AND MEANS FOR CAUSING A SUBSTANTIAL PORTIONOF SAID INJECTED ELECTRONS WHICH ARE IN UNFAVORABLE PHASE WITH RESPECTTO SAID HIGH FREQUENCY FIELDS TO BE REMOVED FROM SAID REGION DURINGMOVEMENT OF SAID INJECTED ELECTRONS WITHIN SAID REGION.